1. Field of the Invention
The present invention relates to an LED control system, and more particularly to an LED control system using a modulated signal.
2. Description of Prior Art
Nowadays, the connection way of the LED lamp string modules is separated into two types: serial-type connection and parallel-type connection. The LED lamp string modules are widely used for decoration of trees, scenery designing, signboard, external walls of the building, and so on, because of small size, long life, low power, rapid response, and strong shake-proof property for the LEDs.
The prior art LED lamp string modules are commonly employed to be connected in series. Also, the amount of the LED lamp string modules is determined according to volume of the decorated objects. In addition, all of the LED lamp string modules are controlled by the same controller which initially controls the first LED lamp string module. Although the LED lamp string modules are easily connected together, the remaining LED lamp string modules behind the abnormal LED lamp string module can not be lighted even only one of the LED lamp string modules is abnormal. That is because the control signal can not be sent to drive all of the remaining LED lamp string modules.
In addition, in operation the parallel-type LED lamp string modules are connected to the controller in parallel. Accordingly, each one of the LED lamp string modules is controlled by the controller through a control line and an address line, respectively. For example, ten control lines and ten address lines need to be used when ten LED lamp string modules are employed to be connected in parallel. Also, the remaining LED lamp string modules can still be normally controlled when one of the LED lamp string modules is abnormal. However, the amount of the control lines and the address lines increase proportionally. Therefore, complexity and costs of the equipment also increase when the amount of the LED lamp string modules increases.
Now matter the connection way of the LED lamp string modules is serial-type or parallel-type, many power transmission lines and signal transmission lines need to be used to control the color and intensity of the LED lamp string modules. Accordingly, cost down can be achieved only if the amount of the power transmission lines or the signal transmission lines can be reduced.